Tumor cell metastasis is the primary cause of death in most cancers. Numerous laboratories have demonstrated a strong correlation between the sialylation of the cell-surface and the propensity of a tumor cell to detach and metastasize. By combining recent advances in the study of cell-surface sialylation with the bio-assays of the B16 murine melanoma system, our plan is to critically evaluate the specific structural basis for sialylation's role(s) in the generation of the metastatic phenotype. These structural/functional studies will provide the foundation to further elucidate the metabolic basis of altered sialylation in highly metastatic tumor cells. The planned systematic approach will involve the use of murine B16 melanoma variants that have widely different metastatic properties or that metastasize to specific organs. Specific Aims are as follows: 1) Several highly purified sialyltransferases and sialidases, of known specificities, will be used as impermeant probes of the cell-surface saccharide topography on living B16 melanoma cells that differ in metastatic potentials. 2)\Glycosylation site specific oligosaccharide microheteogeneity of major sialoglycoproteins or histocompatibility antigens from B16 metastatic variants will be determined. 3) The relationship between a tumor cell's glycosylation state and its target organ specificity will be investigated by comparing the saccharide topography and glycosylation site specific oligosaccharide structures on surface molecules obtained from cells that specifically metastasize to lung, liver, ovary or brain. 4) Specific inhibitors of N-linked oligosaccharide processing, and enzymic modifications of the cell- surface by glycosyltransferases and glycosidases, will be combined with bio-assays of tumor cell metastatic properties to directly evaluate glycosylation's involvement in metastasis. 5) Based upon the structural data, the enzymatic or metabolic cause (eg. glycosyltransferase levels, sugar nucleotide levels, processing enzymes, transport, etc.) of the differential sialylation between highly and poorly metastatic B16 melanoma variants will be determined. These studies are making use of the best model system of tumor metastasis to directly examine the molecular basis of sialylation's role in the process.